1. Many cheaper materials have substances like phthlates, lead, and cadmium that can end up being absorbed by your body. Jelly and Sil-a-Gel have so much chemical ooze that they sting your skin and smell horrible.

Silicone doesn't wear out.
Silicone is nonporous so it can't harbor bacteria/germs.
Silicone can be sterilized if necessary.
Silicone can be cleaned easily with soap and water.
Silicone is skin-friendly. It doesn't ooze bad chemicals.
Silicone is versatile. It comes in different colors,shapes,textures and levels of firmness.

Smooth silicone (no bumps or ridges), especially if it happens to be high quality, soft feeling silicone is my preference. I don't mind the higher price for something that feels nice and will hold up well. The cheaper the quality of the toy (plastic, poorly made, etc), the less I'm willing to pay for it. That being said, some high end toys are still a little too expensive for my liking.

Silicone is absolutely worth it - I will not buy anything else and haven't for about 10 years. The rest of the responses give the details - from my perspective sex is one of the most important aspects of my life - why would I go cheap?

When I buy toys I look for the most expensive 1st - that automatically eliminates the cheap jelly, rubber, PVC and vinyl. But if I can get a better value without sacrificing quality - I will - it just has to be 1st quality silicone. Fun Factory, Vixskin, Tantus, Vamp, Bad Dragon are my go-to brands. I've tried Jimmy Jane and others, but they tend to underperform on the vibration side of the equation.